The target precision for a projectile in an artillery system is governed largely by meteorological aspects and by how closely the actual launch velocity, V0, tallies with the calculated launch velocity, as well as by launcher-dependent factors, such as the configuration of the barrel and the exactness of the aiming system. Before guidable projectiles began to be used in artillery applications, there was no possibility of influencing the trajectory of the projectile after the projectile had left the barrel.
Through the introduction of guide elements, such as a rudder or fins/wings, the guidance capability of a projectile is able to be controlled. Depending on the configuration, placement and size of the fins/wings, different degrees of guidance capability can be achieved. Different guidance capabilities are required, depending on the VO, firing range, trajectory height and target precision of the projectile. For a short firing range and high target precision, guidance capability merely during the end phase of the projectile is sufficient, which means that smaller fins in the front part of the projectile can be used. In the case of a long firing range and high target precision, guidance capability is required during both the gliding phase and end phase of the projectile, which calls for larger fins/wings with high guidance dynamic.
Reliable techniques for calculating the current position of a projectile during its trajectory phase, based on inertial navigation and/or satellite navigation via GPS, have also been developed. For reliable use of satellite navigation techniques or navigation technology based on electromagnetic or optical communication with ground-based transmitters, stable communication between the satellite/the transmitter and the receiver antenna of the projectile is required. It is then advantageous if the receiver antenna is arranged such that it is roll-stable.
Rotationally stabilized projectiles in which the rear part, middle part or front part of the projectile is arranged so as to rotate freely relative to the rest of the projectile in order to stabilize the projectile, and in which the freely rotating part is arranged with guide fins in order to guide the projectile during its gliding and end phase, are previously known.
EP 1 299 688 B1 describes a roll-stabilized guidable projectile, the rear part of which is freely rotating relative to the rest of the projectile body. Guide fins, for guiding the projectile during the end phase, are disposed on the front part of the projectile, i.e. on the part which does not rotate.
US 2005/0056723 A1 describes a guidable rotationally stabilized projectile, the guide fins of which are fixedly disposed on the nose cone of the projectile, which nose cone is rotatably arranged relative to the rest of the projectile body. In a shown embodiment having four guide fins, two of the fins are positioned at an equal yet opposite angle in the axial direction of the fins, in the axis which is formed in the longitudinal direction of the fins radially outward from the projectile body, so that a propeller-like configuration is formed to counter the rotational force from the projectile. The other two fins are positioned at the same angle in the same direction in the axial direction of the fins, in the axis which is formed in the longitudinal direction of the fins radially outward from the projectile body. Once the rotation of the nose cone has been stabilized relative to the projectile body, the two horizontally positioned fins will generate a lifting force, which means that the projectile can be guided.
US 2008/0061188 A1 describes a rotationally stabilized projectile having a rotating middle section with fixedly mounted guide fins. The middle section is used for roll-stabilization and the fins for guidance of the projectile. Roll-stabilization of the middle section is realized purely by braking relative to the projectile body when the moment of inertia in the projectile body is large relative to the middle section.
One problem with the said projectile constructions, especially in the case of long firing ranges, is that the limited fin size results in low gliding capability.
A further problem with the said projectile constructions is that limited guidability sets in when the rotation of the rotationally stabilized projectile decreases in the case of long firing ranges.
Further problems which the invention aims to solve will emerge in connection with the following detailed description of the various embodiments.